Ocean Sciences News

The Deep Blue Sea Is Getting Bluer

Ocean color will intensify in the next century due to global warming altering phytoplankton communities.


The ocean’s aquamarines and seafoam greens are shifting as climate change warms the planet. A study published Monday in Nature Communications predicts that the colors of the world’s oceans will intensify by the end of this century as changes in phytoplankton patterns alter light reflection.

Water molecules absorb all visible light except for those at blue wavelengths, making the ocean appear blue. When phytoplankton float near the surface, they change how incoming light reflects. Typically, the greener the ocean water, the more phytoplankton occur there. Satellites can differentiate subtle changes in hues from hundreds of kilometers away.

Previous research has suggested that warming waters will alter phytoplankton distribution in the ocean, but pinpointing this trend in the data can be difficult because commonly used metrics fluctuate due to other factors like El Niño and La Niña. The latest study models ocean color using a metric that better resolves long-term trends.

The results reveal that the color of 50% of the ocean will change by 2100 due to the shuffling of phytoplankton communities. Blue regions in the subtropics will grow bluer as fewer phytoplankton are able to survive in its waters. Green regions at the poles will turn greener as warming waters become more habitable for them. The color change won’t be discernible to the human eye, the researchers write in the study, but satellites will be able to see an “unambiguous signal.”

Models that include light reflectance as well as the complex physical, biogeochemical, and ecological processes in the ocean are rare. This study is the first to consider the impact of climate change on ocean color.

“It could be potentially quite serious,” said lead author Stephanie Dutkiewicz in a press release. “If climate change shifts one community of phytoplankton to another, that will also change the types of food webs they can support.”

—Jenessa Duncombe (@jrdscience), News Writing and Production Intern

Citation: Duncombe, J. (2019), The deep blue sea is getting bluer, Eos, 100, https://doi.org/10.1029/2019EO115971. Published on 08 February 2019.
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