Oceans are getting greener – MO*

More than half of the world’s oceans have changed color dramatically in the past 20 years, according to international research. Perhaps this is a consequence of global warming.

A satellite spectrometer has been observing the color of the oceans for 21 years, detecting color differences that are too subtle for the human eye. Much of the ocean appears blue, while the actual color may contain a mixture of more subtle wavelengths, from blue to green and even red.

Analysis of those measurements shows that 56% of the ocean’s surface is becoming increasingly green, especially in tropical ocean regions close to the equator. This shift indicates that surface water ecosystems are also changing, because the color of the ocean is a reflection of the organisms and materials in the water.

The color of the ocean indicates what is in the upper layers: dark blue often means very little life, while green water means the opposite. Green mainly refers to phytoplankton: the pigment helps the plankton capture sunlight, thereby capturing carbon dioxide from the atmosphere and converting it into sugars.

Researchers cannot yet determine exactly how marine ecosystems have changed. But they are quite confident that human-caused climate change is the root cause.

predictions

To see if this trend is related to climate change, the results were compared to simulations previously conducted for two scenarios: one with greenhouse gases and one without. The greenhouse gas model predicted a major trend and that trend would cause ocean color changes in about 50% of the oceans – which is exactly what the measurements show.

“It’s scary to see this happen in real life.”

“I’ve run simulations that have told me for years that these changes in ocean color are going to happen,” said MIT researcher Stephanie Dutkiewicz, MIT researcher. So it’s not surprising, but scary to see that happen in real life. These changes are consistent with human-caused changes in our climate.

We can say that the changes in color reflect changes in the plankton communities, which will affect anything that feeds on plankton. It will also affect how much carbon those oceans will absorb, because different types of plankton have different capacities for this.

We hope people take this seriously. It’s not just models that anticipate these changes. We can see that happening now and the ocean is changing.”