Climate crisis makes oceans change color and signals threat to life, says study

The color of the oceans changed significantly in the last 20 years, probably because of the climate changes caused by man. The information is in a study published on Wednesday (12) in the journal “Nature”.

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

Tropical oceans near the equator, in particular, have become greener over the past two decades, reflecting changes in their ecosystems.

The ocean’s color arises from the materials found in its upper layers. A deep blue sea, for example, has very little life, while a green color means that there are ecosystems, based on phytoplankton, plant-like microbes that contain chlorophyll. Phytoplankton forms the basis of a food chain that supports larger organisms such as krill, fish, and marine birds and mammals.

It’s unclear exactly how these ecosystems are changing, said study co-author Stephanie Dutkiewicz, a senior research scientist in the Department of Earth, Atmospheric and Planetary Sciences at MIT and the Center for Global Change Science. While some areas are likely to have less phytoplankton, others have more – and it is likely that all parts of the ocean will see changes in the types of phytoplankton present.

Ocean ecosystems are finely balanced and any change in phytoplankton has an impact on the food chain. “All the changes are causing an imbalance in the natural organization of ecosystems. It will only get worse over time if our oceans continue to warm.” CNN .

The changes will also affect the ocean’s ability to act as a carbon sink, Dutkiewicz said, as different types of plankton absorb different amounts of carbon.

Researchers are still working to understand what the changes mean, but what is already clear is that the changes are being driven by human-induced climate change.

“Clear trend”

The researchers monitor changes in ocean color from space by tracking the amount of green or blue light reflected from the sea surface.

The data comes from the Aqua satellite, which has been monitoring water color changes for over two decades and is able to pick out differences that are not visible to the human eye.

Color variation data from 2002 to 2022 was analyzed and then models of climate change were created to simulate what would happen to the oceans, both with more pollution from global warming and less.

The color changes matched almost exactly what Dutkiewicz predicted would happen if greenhouse gases were added to the atmosphere: that around 50% of our oceans would change color.

The scientist, who has been running simulations that show the oceans will change hue for years, said she was not surprised by the discovery.

“But I still found the results very worrying; it is another wake-up call that human-induced climate change has significantly impacted the earth system,” he opined.

Dutkiewicz told CNN that it was difficult to say whether the changes would become visible to humans if the process continued.

“If a big tipping point is reached in some places, maybe it will be visible. But you have to study colors for a long time to be able to pick up on those changes,” she explained.

The researcher’s next step is to try to better understand the changes in color in different regions of the ocean, as well as to look for the cause of this change.