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Seas will change colour as climate heats up

06 February 2019

These changes should be observable from orbit, the authors add, meaning satellites could be used as an early warning system against wide-scale changes in marine ecosystems. Their model can estimate wavelengths of light that are absorbed and reflected by the ocean, which obviously changes by a given region and the organisms in the water.

"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 Dr Dutkiewicz. "That basic pattern will still be there". Still, the sweeping alterations to sea life will be significant enough to affect ocean's food web, which phytoplankton sit at the base of. She made a decision to try a new method: looking a subtle shifts in water color.

The team allowed their model to simulate conditions up to the end of the present century. The effect will be in the coming time, these species will get extinct and predictions are by 2100, more than 50% of world's seas will change their colors and get more blue.

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.

Some regions that are greener now are expected to turn a deeper hue due to climate change as more diverse phytoplankton brew up in warmer temperatures.

The simulations, which take about three weeks to run on a large array of computers, revealed we can expect our oceans to look a little different in the future, though it depends on where you go.

Water molecules can not soak up blue portions of the spectrum, reflecting it back out giving more desolate waters a deeper blue appearance. Thus, there are more chances of green regions to appear near the poles and equators, study says. Organisms in the water tend to change this overall color, as they absorb and reflect different wavelenghts of light.

The research team found their model's predictions matched the spectral signatures measured by satellites. 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.

"Sunlight will come into the ocean, and anything that's in the ocean will absorb it, like chlorophyll", Dutkiewicz says.

A particularly-swirly Phytoplankton bloom off the coast of South Africa, near where the South Atlantic meets the Southern Indian Ocean. They are home to a stunning range of lifeforms of all shapes and sizes, all of which have unique properties and reflect different wavelengths of light.

This new study models the likely impact these changes will have on the colour of the ocean and the planet as the world warms up. That gets reflected back out, giving it its deep blue color.

The model's results were compared to actual measurements of ocean-reflected light taken in the past. 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. According to Nasa, warming changes key properties of the ocean and can affect phytoplankton growth, since they need not only sunlight and carbon dioxide to thrive, but also nutrients.

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

Dutkiewicz says ocean warming is already changing the types of phytoplankton and where they live.

Seas will change colour as climate heats up