People who love the ocean know it can be blue, green or gray, depending on the weather. It’s a different color in the tropics than here in New England or up in the Arctic.
But here’s a factor most people probably have not considered when it comes to ocean color: climate change.
New work using satellite photos suggests that the color of the ocean could change significantly over the next few decades, with the subtropics turning bluer and the Arctic and Antarctic turning greener as ocean waters warm.
And this is far from a cosmetic issue. It’s a reflection of fundamental changes in ocean chemistry and ecosystems.
“It can tell us about the amount of phytoplankton that are in the ocean,” Stephanie Dutkiewicz told Living Lab Radio. Dutkiewicz is a principal research scientist at the Massachusetts Institute of Technology and lead author of the study in the journal Nature Communications.
“Phytoplankton are at the base of the food web, the sort of plants of the ocean,” she said. “They take up sunlight and make organic matter, and that feeds everything else that are in the oceans.”
When the ocean appears green, what we're seeing is the phytoplankton's chlorophyll.
Satellite photos show Dutkiewicz and her colleagues what types of phytoplankton are in the ocean based on subtle differences in color.
She hasn't detected any unusual changes in the location of phytoplankton yet. But using this technique to create a model, she expects to see bluer waters in places like Hawaii, and greener waters near the top and bottom of the globe.
Phytoplankton won't completely die off even if the oceans get pretty hot, Dutkiewicz said. But there will be changes to what types survive, and that's going to affect the rest of the food web because it will force ocean animals to adapt quickly — perhaps more quickly than they are able to.
Dutkiewicz used a land-based example.
“If you suddenly started having cactuses growing where there’s [now] only grass, you can imagine all the insects and all the mammals that are used the grassland would not really know what to do with a cactus,” she said.
“As you go up to things like polar bears … they may not be able to get the food that they are used to because we've altered what's happening at the bottom of the of the food chain.”
Dutkiewicz acknowledged that models are not going to perfectly capture reality.
“But we can use them as a laboratory to begin to explore what will happen in the future world,” she said.
