A new study finds that climate change is causing our oceans to change colour

CNN
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A new study shows that the color of the ocean has changed dramatically over the past 20 years and human-caused climate change is likely to blame.

More than 56% of the world’s oceans have changed color to an extent that cannot be explained by natural variability, said a team of researchers led by scientists from the National Oceanography Center in the United Kingdom and the Massachusetts Institute of Technology in the United States. a permit.

Tropical oceans near the equator in particular have become greener in the past two decades, reflecting changes in their ecosystems, according to the study published Wednesday in the journal Nature.

The color of the ocean is derived from the materials in its upper layers. For example, a deep blue sea would have little life in it, while green would mean there are ecosystems there, based on phytoplankton, and plant-like microbes that contain chlorophyll. Phytoplankton form the basis of the food web that supports larger organisms such as krill, fish, seabirds, and marine mammals.

It’s not clear exactly how these ecosystems are changing, said study co-author Stephanie Dutkiewicz, a senior investigator in MIT’s Division of Earth, Atmospheric, and Planetary Sciences and the Center for the Science of Global Change. While some areas are likely to have fewer phytoplankton, others have more – and all parts of the ocean are likely to see changes in the types of phytoplankton present.

Ocean ecosystems are well balanced and any change in phytoplankton will send ripples down the food chain. “All changes disrupt the natural organization of ecosystems. This disruption will only get worse over time if the oceans continue to warm,” she told CNN.

It would also affect the ocean’s ability to act as a carbon store, Dutkiewicz said, as different plankton absorb different amounts of carbon.

While the researchers are still working out exactly what the changes mean, what is clear, they said, is that the changes are being driven by human-induced climate change.

Researchers Observed changes in ocean color from space by tracking the amount of green or blue light reflected from the sea surface.

They used data from the Aqua satellite, which has been monitoring ocean color changes for more than two decades and is able to identify variations invisible to the human eye.

They analyzed color contrast data from 2002 to 2022 and then used climate change models to simulate what might happen to the oceans with and without additional pollution from a warming planet.

The color changes matched almost exactly what Dutkiewicz predicted would happen if greenhouse gases were added to the atmosphere—that is, about 50% of our oceans would change colour.

She wasn’t surprised by the discovery, said Dutkiewicz, who has been running simulations that showed the oceans would change color for years.

But I still found the results very realistic; another wake-up call that human-caused climate change [has] “It has greatly impacted the Earth system,” she told CNN via email.

Dutkiewicz told CNN that it is difficult to say whether the color changes could become visible to humans if the process continued.

“If a big turning point is reached in some places: maybe. You will have to study the colors for a while to be able to recognize the changes,” Dutkiewicz said.

Next, Dutkiewicz will try to better understand the color changes in different regions of the ocean, as well as look at what might be causing them, she said.