Saturday, September 30, 2023

Climate change is altering the color of the ocean: it reflects changes in ecosystems

Although our eyes do not perceive it with the naked eye, in the last twenty years the ocean color has changed significantly and, according to a study published in Nature, this alteration is a consequence of climate change caused by man.

The study, led by scientists from the Massachusetts Institute of Technology (MIT) and the National Oceanography Center of the United Kingdom, points out that this change has been detected in 56% of the world’s oceans, an area greater than the total land area from the earth.

The article explains that tropical ocean regions near the equator are becoming greener, indicating that the ecosystems of the surface are also changing, since the color of the ocean is a “literal” reflection of the state of the organisms and materials in its waters.

The researchers still can’t say exactly how marine ecosystems are changing, but they’re sure it’s caused by the climate change.

“For years I have been carrying out simulations that indicate that these changes in the color of the ocean are going to occur. See what’s happening It’s no longer amazing, it’s terrifyingsaid Stephanie Dutkiewicz, a co-author of the study and a research scientist at MIT.


The color of the ocean reflects what is in the upper layers: deep blue waters reflect very little life, and greener waters indicate the presence of ecosystems, mainly phytoplankton -plant-like microbes that abound in the upper layers of the ocean-.

He phytoplankton it is the foundation of the marine food web that supports progressively more complex organisms, up to and including krill, fish, and marine birds and mammals, and is also a powerful muscle in the ocean’s ability to capture and store carbon dioxide.

That’s why scientists have spent decades monitoring phytoplankton on the ocean’s surface and studying how these essential communities respond to climate change, monitoring from space.


Cael and his team analyzed measurements of ocean color made by the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellitewhich has been monitoring the color of the ocean for 21 years and makes measurements at seven visible wavelengths.

And it is that, although much of the ocean appears blue to our eyes, the real color can contain a mixture of more subtle wavelengths, from blue to green and even to red.

Cael made a statistical analysis jointly using the seven ocean colors measured by the satellite between 2002 and 2022. He first looked at how much the seven colors changed from one region to another over a year, and then extended the analysis to two decades.

The analysis revealed a clear trend, above the normal annual variability.

To see if the trend is related to climate change, he turned to Dutkiewicz’s 2019 model, which simulates Earth’s oceans in two scenarios: one with the addition of greenhouse gases and one without.

The kind of greenhouse gases predicted that a significant trend should appear in 20 years and that this trend should cause changes in the color of the oceans in about 50 percent of the world’s surface oceans (exactly what Cael found in his analysis of satellite data from the world real).

“The color of the oceans has changed, because it reflects changes in plankton communities, which will affect everything that feeds on plankton.”

“Those changes will also change how much carbon the ocean will absorb, because different types of plankton have different abilities to do so. So we hope people take it seriously. Not only models predict these changes. Now we can see it, and the ocean is changing,” Dutkiewicz said.

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