| 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. 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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