Feeling blue?

Going Green

Climate change is not only making our oceans hotter — it's likely causing them to change color, too.

This potentially massive revelation is according to new research published in the journal Nature, which suggests that our oceans are gradually becoming greener over time, and have been for at least the past two decades.

"The reason we care about this is not because we care about the color, but because the color is a reflection of the changes in the state of the ecosystem," lead author BB Cael, a scientist at the National Oceanography Center at the University of Southampton, told The Guardian.

Plankton Pointer

Changes in ocean color can be driven by manifold factors, but scientists tend to focus on phytoplanktons, which form the bedrock of the ocean's ecosystem and are found near the surface.

Phytoplanktons contain the green pigment chlorophyll, and as such, tracking the changes in the green hues they reflect from sunlight has served as the go-to indicator of their population, and thereby the ocean's health.

But this method has its shortcomings. Specifically, chlorophyll levels tend to swing naturally year-to-year, leading some scientists to believe it would take some 40 years of observations before a trend could be spotted, according to Nature.

Cael's team sidestepped this by observing colors across a fuller spectrum, encompassing more than just green. For this, they turned to NASA's Aqua satellite, and scoured through over 20 years' worth of its data and compared it to a computer model that simulated the ocean's changes without climate change.

Their findings? That over 56 percent of the world's ocean surface has noticeably shifted in color, generally getting greener.

Boiling Point

According to the data, while most areas trend greener, some have shown shifts in the red and blue spectrums, too. Overall, these shifts in color match the predictions of a simulation of how the ocean might respond to rising levels of greenhouse gases — a compelling link to climate change, though one that could use bolstering in future studies.

Still, Cael says it's possible that these shifts may not be directly driven by warming temperatures. Instead, the warming could be making it harder for nutrients to reach the phytoplanktons, changing the makeup of their populations and somehow affecting the ecosystem at large. But for now, scientists can't know for sure.

"These are not ultra, massive ecosystem-destroying changes, they may be subtle," Cael told The Guardian. "But this gives us an additional piece of evidence that human activity is likely affecting large parts of the global biosphere in a way that we haven't been able to understand."

More on climate change: Antarctic Ice Reaches "Record-Smashing Low," Alarming Scientists

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