Original photo by Mickey O'neil/ Unsplash
Climate change isn’t just raising the temperature of the world’s oceans — it’s also changing their color. As the oceans absorb the excess heat generated by greenhouse gases, that heat is altering the aquatic life in their waters. New research published in Nature in 2023 shows that the familiar blue hue of the oceans has been steadily transforming over the past 20 years into a greener shade, especially in tropical and subtropical areas of the world.
Oops, incorrect!
It's a factEvery night, trillions of sea creatures called zooplankton travel to the ocean’s surface to feed on photosynthesizing phytoplankton. Although the distance for some organisms is only 1,000 feet, that’s the equivalent of a human swimming 50 miles in an hour.
The color of the ocean is dependent on a variety of factors, but one key is the light absorption of H2O. Water usually readily absorbs longer wavelengths of light — red, yellow, and green — and scatters blue. However, a concentration of marine life can cause emerald waters. The newly green hue detected by the 2023 research likely reflects a change in the ocean’s phytoplankton — the algae responsible for 70% of the world’s oxygen, and which also provides the foundation for the marine food web. Scientists monitored ocean color using NASA’s Aqua satellite, and found marked shifts toward green in about 56% of the world’s oceans between 2002 and 2022. Statistical simulations showed that added greenhouse gases are to blame, although it’s not exactly clear how, since areas that warmed the most at the surface weren’t the ones that turned green the most. Some scientists theorize that the change may have to do with reduced mixing in the layers of ocean water, caused by the heat, which limits the nutrients that rise to the surface and consequently affects the types of plankton that can survive. But don’t go color-correcting your photos just yet: While satellites can detect the change in ocean hue, the change is slight enough that most humans probably wouldn’t notice a difference.
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The world’s cleanest and clearest large body of water is the U.S.’s ______.
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The world’s cleanest and clearest large body of water is the U.S.’s Crater Lake.
Human eyes are most sensitive to the color green.
Human eyes can only perceive a small fraction of the electromagnetic spectrum. The visible spectrum, which excludes things like radio waves, X-rays, infrared, ultraviolet, and (very dangerous) gamma rays, stretches from around 380 nanometers (nm) to about 740 nm. Glimpse a rainbow — or recite the elementary school acronym ROYGBIV — and you’ll notice that green lies right in the middle of our visual sweet spot. The color occupies around 520 to 565 nm, and the light sensitivity of the human eye in daytime peaks at about 555 nm, which is a green that’s close to yellow. Because of this advantageous middle-of-the-road placement, the human eye can discern more shades of green than any other color. Since seeing green is also less of a strain on our visual system, the color positively affects our mood — essentially, our nervous system gets to relax. Green’s innate ability to “placate and pacify” is one reason the hue can often be found in places of healing, especially hospitals.
Darren Orf lives in Portland, has a cat, and writes about all things science and climate. You can find his previous work at Popular Mechanics, Inverse, Gizmodo, and Paste, among others.
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