By 2100, oceans would become more greener and bluer

Birdseye shot of green ocean creating waves on a sandy beach

Birdseye shot of green ocean creating waves on a sandy beach

The lead author says the ocean will still reflect the basic "blue" color palette we now see, but the blue areas like the subtropics will look more blue, and greener regions near the poles will be more green.

The changes, caused by shifts in populations of tiny marine plants known as phytoplankton, may not be detectable by the naked eye but will affect the appearance of oceans when photographed by satellites.

Writing in the journal Nature Communications, Hickman and colleagues from the United Kingdom and USA report how they came to their conclusions by using a computer model that predicts how factors such as temperature, ocean currents and ocean acidity affects the growth and types of phytoplankton in the water, as well as levels of other coloured organic matter and detritus. The phytoplankton's chlorophyll, which absorbs blue and reflects green.

Essentially, climate change will make the blues of the ocean bluer and the greens greener.

"Phytoplankton are the base of the food web-less phytoplankton [means] less food for the rest of the marine ecosystem", study co-author Stephanie Dutkiewicz, a principal research scientist in MIT's Department of Earth, Atmospheric, and Planetary Sciences, told in an email. "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".

Climate change will bring a color change to half of the world's oceans by the end of the21st century, the study says.

Phytoplankton are primary producers of energy: Using chlorophyll, they convert sunlight into energy, thus feeding an entire food chain above them.

Writing in Nature Communications, researchers report that they have developed a global model that simulates the growth and interaction of different species of phytoplankton, or algae, and how the mix of species in various locations will change as temperatures rise around the world. Regions that are nutrient-rich, including those near the poles, "may turn even deeper green, as warmer temperatures brew up larger blooms of more diverse phytoplankton". Climate change will fuel the blooming of some phytoplankton in some areas, while reducing it in other spots, leading to subtle changes in the ocean's appearance.

What the new hues will essentially reflect is life in those regions.

In total, climate change will alter at least 30 percent of the ocean's color by 2100 and perhaps more than 60 percent, the researchers say. By looking at these measurements, the level of chlorophyll can be determined, which could be due to global warming or weather-related phenomena, such as an El Niño or La Niña, Dutkiewicz said.

But in the scientific world, they could mean significant shifts. Dutkiewicz fed satellite measurements of reflected light into a computer model, and correlated it to the number and type of ocean organisms.

When they increased the global temperatures by up to 3 degrees Celsius by 2100, they found that wavelengths of light in the blue or green wave band responded the fastest. The sensors, which measure the colour of the water, work to calibrate satellite data in real time, providing information about the health of the Salish Sea.

For Mr. Strutton, "What this study has shown is that although the greenness of the oceans, the amount of chlorophyll might only be changing by small amounts, what's important is that the type of phytoplankton might be changing more dramatically". By the end of the century, our blue planet may look visibly altered.

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