Science

The colour of the oceans could be about to change

The colour of the oceans could be about to change

For the study, the researchers developed a global model that simulates the growth and interaction of different species of phytoplankton.

According to Dr Dutkiewicz, "By the end of 21 century, a difference in the color by 50% would be noticed".

"The basic pattern will still be there", said Research Scientist Stephanie Dutkiewicz in a press release from MIT. "Phytoplankton are at the base, and if the base changes, it endangers everything else along the food web, going far enough to the polar bears or tuna or just about anything that you want to eat or love to see in pictures".

Dutkiewicz's co-authors include Oliver Jahn of MIT, Anna Hickman of the University of Southhampton, Stephanie Henson of the National Oceanography Centre Southampton, Claudie Beaulieu of the University of California at Santa Cruz, and Erwan Monier, former principal research scientist at the MIT Center for Global Change Science, and now assistant professor at the University of California at Davis, in the Department of Land, Air and Water Resources. Thus, more quantity of phytoplankton, lesser the blue color in the sea and more of green shaded water.

According to Nasa, when sunlight hits the ocean, some of the light is reflected back directly, but most of it penetrates the ocean surface and interacts with the water molecules it encounters. Climate change is altering the ocean currents, meaning there will be fewer nutrients for phytoplankton to feed on in some areas, so there will be a decline in their number in those regions.

The ocean is rich in diverse shades of blue and green.

Phytoplankton, for instance, contain chlorophyll, a pigment which absorbs mostly in the blue portions of sunlight to produce carbon for photosynthesis, and less in the green portions.




Since the 1990s, satellites have taken regular measurements of how much chlorophyll is in the ocean. By keeping a close watch on ocean colours, scientists can better understand phytoplankton and how they impact the world around them. Those levels can change because of weather events or because of climate change.

The colour of the oceans could be about to change. "I would probably predict that the colour change isn't going to be perceptible to the naked eye", said Hickman.

While these changes may seem small, scientists say that they are deep and long-lasting. "So it's a complicated process, how light is reflected back out of the ocean to give it its color". These organisms are responsible for much of the colour we see.

When global temperatures increase by 3°C, which most scientists expect to occur by 2100, they found light in the blue and green waveband respond the fastest, but climate-driven changes to chlorophyll could begin as soon as 2055.

But it's been hard to detect and measure these changes, says Dutkiewicz, partly because there's so much variability in the ocean from year to year. "But you can see a significant, climate-related shift in some of these wavebands, in the signal being sent out to the satellites". But using those images to look at reflected light alone, the researchers in the new study could distinguish what is specifically due to climate change.

The study, published Monday in the journal Nature Communications, offers a new way to predict these changes, a model which could serve as an early warning signal for ocean health. "It could be potentially quite serious". Thus, the climate change would bring a major change in quantity of phytoplankton in the ocean, as a result, support provided by this element to different types of food chains will get affected.