Jakarta –
One of the natural signs due to significant climate change is the change in color in the marine ecosystem. MIT campus scientists report that the color of the ocean has changed significantly over the past 20 years.
In a study on Naturethe research team writes that they have detected changes in the color of the ocean over the past two decades that cannot be explained solely by natural variability from year to year.
This color shift, although imperceptible to the human eye, has occurred in more than 56 percent of the world’s oceans.
According to researchers at the National Oceanographic Center in England, this global trend is most likely a consequence of human-caused climate change.
Tropical Seas Near the Equator Are Getting Greener
In particular, the researchers found that tropical ocean areas near the equator have become greener over time.
The shift in the color of the oceans indicates that the ecosystems on the surface of the oceans must also change, because the color of the oceans is a literal reflection of the organisms and materials in the waters.
At this point, researchers can’t say how exactly the marine ecosystem changed to reflect the change in color. But they’re pretty sure that human-caused climate change is most likely to blame.
“I’ve been running simulations that have been telling me for years that this change in the color of the oceans is going to happen,” said Stephanie Dutkiewicz, a senior scientist in MIT’s Department of Earth, Atmospheric, and Planetary Sciences and Center for Global Change Science, quoted from MIT’s official website.
“To actually see it happening for real is not surprising, but frightening. And these changes are consistent with human-caused changes to our climate.”
Lead author from the National Oceanographic Center in Southampton, England, BB Cael PhD also said the same thing. Changes in the color of the ocean provide additional evidence of how human activities affect life on Earth at enormous spatial scales.
“This is another way humans are influencing the biosphere,” he said.
The study’s co-authors also include Stephanie Henson of the National Oceanography Center, Kelsey Bisson at Oregon State University, and Emmanuel Boss of the University of Maine.
How to See the Changing Color of the Ocean?
In the current study, Cael and his team analyzed measurements of ocean color taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Aqua satellite, which has been monitoring ocean color for 21 years.
MODIS takes measurements in seven visible wavelengths, including the two colors that researchers typically use to estimate chlorophyll.
The color differences picked up by satellites are too subtle for the human eye to distinguish. Most of the ocean appears blue to our eyes, whereas its true color may contain a finer mix of wavelengths, from blue to green and even red.
Cael performed a statistical analysis using all seven ocean colors measured by satellite from 2002 to 2022 together.
He first saw how much the seven colors changed from region to region during a given year, which gave him an idea of their natural variation.
Then he zoomed out to see how this annual variation in sea color has changed over the two decades. This analysis yields clear trends, above normal year-to-year variability.
To see if this change in ocean color was related to climate change, he then looked at Dutkiewicz’s model from 2019. This model simulated Earth’s oceans under two scenarios: one with added greenhouse gases, and the other without added greenhouse gases.
Greenhouse gas models predict that a significant trend will emerge within 20 years and that this trend will cause a change in the color of the oceans on about 50 percent of the world’s ocean surface.
That is, it is almost exactly what Cael found in his analysis of real-world satellite data.
“This suggests that the trends we are observing are not random variations in the Earth system. They are consistent with anthropogenic climate change,” said Cael.
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2023-07-22 05:00:00
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