Three possible outcomes from East China Sea oil spill, according to Chinese scientists

As the authorities battle to clean up toxic fuel leaking from the sunken wreckage of Iranian oil tanker Sanchi, scientists are looking at how the spill may affect the region and beyond.

The vessel was carrying nearly one million barrels of ultralight, highly flammable crude oil when it collided with a freighter east of Shanghai on January 6.

After burning for about a week, it exploded and sank 150 metres (492 feet) to the seabed midway between Zhejiang province and Japan’s Ryukyu Islands on Sunday.

As the oil slick continues to spread, its possible environmental impact could be limited or it could see trace pollutants reaching as far as the west coast of North America.

Here are three possible scenarios, based on interviews with Chinese government scientists.

Seafood supply may be hit as Sanchi oil spill spreads in East China Sea

1. Trace pollutants could reach US shores

Some trace pollutants from the Sanchi could ride sea currents and reach as far as the west coast of North America, according to Chinese government scientists.

The location of the wreckage, which is likely still leaking, is dozens of kilometres away from the Black Tide, or Kuroshio current. The Black Tide is as strong as the Gulf Stream in the Atlantic Ocean and transports warm, nutrition-rich water from west of the Ryukyus, north to Japan’s main islands.

It is connected to the North Pacific Current, which heads east to British Columbia, Canada where it splits into two courses – one going north to Alaska and the other turning south to California.

Pollutants from the Sanchi could be carried by some of the most powerful ocean currents, according to Zhu Xiaohua, a researcher at the Second Institute of Oceanography, State Oceanic Administration in Hangzhou, Zhejiang.

The trans-Pacific current, for instance, is driven by powerful eastbound winds that can reach up to two metres per second (6.56 feet per second) or over seven kilometres per hour (4.35 miles per hour), Zhu said.

“It will definitely be possible to detect some pollution particles from the Sanchi along America’s west coast in the future,” he said.

Marine physicist Zhou Feng, who is also from the institute – China’s largest government body researching offshore pollution – agreed with Zhu.

“The site where the tanker sank is indeed quite close to the Black Tide,” he said, adding that the East China Sea in winter was dominated by northern winds, which could carry the tainted water into the current.

2. Environmental damage could be limited within the region

But Zhou said he believed the negative impact to the environment was likely to be limited within the East China Sea, especially around the wreckage.

Pollutants could affect the marine ecosystem including fishery resources, though further investigation was needed to assess the extent of the impact, he said.

As wind directions changed from day to day, there was also a chance that the spill might move towards other countries such as China and Korea, he said.

But tracking the spread of the pollution could be challenging, according to Zhou. China has fewer pollution monitoring buoys in the area than in other parts of the East China Sea because of its proximity to waters controlled by Japan.

The Chinese government on Monday said the spill was being tracked with satellites and planes, but they will not be able to detect what is happening below the surface.

Predicting the movement of the spill could also be difficult. “Most of our spill simulation models do not cover this area – it’s too far away from the Chinese mainland,” Zhou said.

High alert for huge oil slick in East China Sea, but how bad will it be?

3. Damage could be negligible

Guan Weibin, an offshore biology researcher at the Hangzhou-based institute, said the actual damage to the environment could turn out to be quite small.

“If the Black Tide can carry the remaining oil spill to the Pacific Ocean, it will be good news,” he said.

All of the oil carried by the tanker could be easily diluted in the vast, deep Pacific Ocean, according to Guan.

“A million barrels sounds like a lot, but it is negligible compared to the size of the Pacific Ocean,” he said.

The 136,000 tonnes of oil on the Sanchi was condensate – a transparent form of crude oil that quickly evaporates under moderate temperature.

“Condensate is lighter than water. It tends to surface, then evaporate into the atmosphere,” he said.

“It will be extremely difficult to detect traces of the oil spill on the other side of the Pacific – unless the ship was loaded with other types of oil,” Guan said.

Burning Iranian tanker explodes and sinks, ‘no hope of finding crew alive’