Climate change will dramatically alter colour of Earth’s oceans

4 Feb 2019

Image: © rouda100/

As the delicate ecosystems of the world’s oceans become altered in the face of climate change, so too will their colour.

In one of the starkest forecasts about climate change so far, MIT researchers have warned in Nature Communications that skewed ocean temperatures are causing significant change to the tiny creatures known as phytoplankton. Over the coming decades, these changes will drastically alter the oceans’ colour, intensifying the blue and green hues – this could act as an early warning system for future catastrophe.

To determine this, the research team developed a global model that simulates the growth and interaction of phytoplankton and how the different species mix with a rise in temperatures as well as how the creatures absorb and reflect light.

Phytoplankton contain chlorophyll, a pigment that mostly absorbs in the blue portions of sunlight to produce carbon for photosynthesis, and less so in the green portions. As a result, more green light is reflected back out of the ocean, giving algae-rich regions a greenish hue.

By simulating the world’s oceans up until the year 2100, the model showed that more than 50pc of the oceans will become brighter, with the subtropics becoming more blue, indicating a lack of phytoplankton – and life itself – within the water. Some regions that are greener today, such as near the poles, may turn even deeper green, as warmer temperatures brew up larger blooms of more diverse phytoplankton.

‘It could be potentially quite serious’

“The model suggests the changes won’t appear huge to the naked eye, and the ocean will still look like it has blue regions in the subtropics and greener regions near the equator and poles,” said lead author Stephanie Dutkiewicz. “That basic pattern will still be there. But it’ll be enough different that it will affect the rest of the food web that phytoplankton supports.”

The model that predicted the major colour change was based on the business-as-usual scenario whereby global average temperatures would be three degrees Celsius warmer in 2100 than they are today if no serious climate action is taken.

“It could be potentially quite serious,” Dutkiewicz added. “Different types of phytoplankton absorb light differently and if climate change shifts one community of phytoplankton to another, that will also change the types of food webs they can support.”

Colm Gorey was a senior journalist with Silicon Republic