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Optical satellite image of an oil slick after the "Deepwater Horizon" disaster in the Gulf of Mexico (April 2010)
Photo: REUTERS/DigitalGlobe
They know no bad weather and no break.
Radar satellites keep our earth in view at all times.
They can see through clouds from 700 kilometers up and don't need daylight to see their target.
Among other things, they can monitor sea-level rise and ground movements due to pumped-out groundwater reservoirs, but also – as a by-product – identify the locations of certain military radar installations because they jam the satellites.
Researchers led by Yanzhu Dong and Yongxue Liu from Nanjing University in China have now used the technology to take a closer look at pollution on the world's oceans in images from the European satellites "Sentinel-1A" and "Sentinel-1B".
With the help of artificial intelligence, they were able to identify more than 450,000 oil slicks, including comparatively small amounts of contamination.
The oil slicks recorded between 2014 and 2019 alone added up to a total area of 1.5 million square kilometers - that's more than twice the area of France.
Apparently important role of the growing shipping traffic
When evaluating the data, the team found that a far larger part of the pollution than previously known is caused by humans.
At around 94 percent, the overwhelming majority can be traced back to human activities, such as releases from ships, offshore rigs or pipelines, the group reports in the journal Science.
Previously, for the period 1990 to 1999, it was estimated that about half of the oil spills on the world's oceans were due to natural leaks in the seabed.
According to the current evaluation, it is only around six percent.
One reason is probably the sharp increase in shipping traffic over the past few decades, explains Ira Leifer from the green tech company Bubbleology Research International in an accompanying commentary on the study.
According to the study, the vast majority of the pollution was located within 160 kilometers of coasts and along shipping routes.
The severely affected marine areas included the Java Sea, the South China Sea and the Gulf of Guinea.
Major satellite down
Crude oil is a major problem for the sensitive ecosystems in the oceans: even a small amount can have a major impact on plankton, which form the basis of nutrition in the oceans.
Other marine animals such as whales and sea turtles are harmed when they come in contact with the oil while breathing.
The Sentinel-1A satellite was recently in grave danger of colliding with space debris created by a Russian weapons test last year.
Particles resulting from the shooting down of the defective Soviet satellite "Kosmos 1408" also regularly cause problems for the International Space Station.
The satellite was saved by an emergency evasive maneuver.
The twin satellite »Sentinel-1B« has been out of service since December last year due to a technical problem.
A sequel is expected to launch next year.
chs/dpa