Phytoplankton blooms in the South Pacific Ocean around New Zealand captured by NASA’s Aqua satellite on October 23, 2022. (Image provided by Oregon State University)

Surface waters in more than half the world’s oceans have been changing color during the last two decades due to human-caused climate change, researchers found.

The findings, published in the journal Nature, show that ecosystems supporting all kinds of microorganisms close to ocean surfaces are changing due to climate change. Those microorganisms, along with particles and water molecules on surface water, absorb and scatter light, creating the ocean colors we detect with human eyes. When there is an increase in organisms such as green phytoplankton near the water’s surface, it appears more green.

The researchers aren’t sure how these surface water ecosystems are changing across the world’s oceans, but they said the color shifts indicate the changes are not natural and are not the result of other year-to-year variables such as weather events and currents. 

The findings from the satellite data were corroborated by a climate change model developed at MIT in 2019. The model simulates the planet’s oceans over time with and without the addition of greenhouse gas emissions, and it predicted that within 20 years, about half of the earth’s oceans would begin changing colors. 

The ocean color changes are subtle, but are greatest near the equator, where waters have been turning increasingly green. Scientists believe this is likely due to the proliferation of phytoplankton and zooplankton, which are red, black and green. Ocean colors appear to be changing in parts of the Pacific Ocean along most of the West Coast, including a bit of southern Oregon. 

Kelsey Bisson, an Oregon State professor and oceanographer, worked with the team studying 21 years of satellite imagery and data from a NASA satellite called Aqua, which collects measurements of light from the planet’s oceans. Other researchers came from the U.K’s National Oceanography Center, MIT and the University of Maine.

Bisson said the findings could play a role in protecting ocean health.

“Being able to quantify detectable trends from satellites opens up many new avenues of research that are also relevant for policy changes, such as legal protection against certain activities on the high seas,” she said in the news release.


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Alex Baumhardt has been a national radio producer focusing on education for American Public Media since 2017. She has reported from the Arctic to the Antarctic for national and international media, and from Minnesota and Oregon for The Washington Post. She previously worked in Iceland and Qatar and was a Fulbright scholar in Spain where she earned a master's degree in digital media. She's been a kayaking guide in Alaska, farmed on four continents and worked the night shift at several bakeries to support her reporting along the way.