Climate change is actually changing the color of the ocean

Mindy Sparks
February 5, 2019

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.

In the interim, Dutkiewicz said, paying close attention to changes in the oceans' colour can offer the first clues of the changes that are underway.

"What this study is trying to explain is that in parallel to measuring the amount of phytoplankton in the water, we should also be measuring the light coming from the water", Maycira Costa, professor and coastal oceanography researcher at the University of Victoria, told CTV News. Nitrogen also plays a key role in regulating the global carbon cycle.

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

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. The deeper blue regions will indicate less phytoplankton and therefore less marine life.

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. They consume carbon dioxide and release oxygen.

"Other things will absorb or scatter it, like something with a hard shell". She says that current methods for monitoring phytoplankton provide information about local or regional changes but this new method, which uses satellite data, may offer a clearer, better picture of ocean change. "So it's a complicated process, how light is reflected back out of the ocean to give it its color".

The ocean looks blue or green to us because of a combination of how sunlight interacts with water molecules and with whatever else lives in that water. The resulting model can be fed with various values of inputs, primarily global temperatures.

"What we've shown is that the colour in the blue-green range is going to show that signal of change sooner, in some places in maybe the next decade", said Dr Dutkiewicz.

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. "But you can see a significant, climate-related shift in some of these wavebands, in the signal being sent out to the satellites".

Importantly, she said, the shift in reflectance of blue/green light appeared to give an earlier indication of changes to phytoplankton than estimates of the amount of chlorophyll present, a measure now used to monitor phytoplankton levels.

As well as changes in the blue of the oceans, we are also likely to see changes in the green.

"We're not going to suddenly go from having a blue ocean to a red ocean or something like that, but there will be very, very subtle changes", says Dutkiewicz, a principal research scientist at MIT's Center for Global Change Science. "It could be potentially quite serious".

That, the researchers said, was probably down to a number of factors, including that shifts in ocean colour take into account not only changes in the overall amount of phytoplankton - which can vary dramatically, for example with the season - but also changes in the species present, an important consideration since different types of phytoplankton use chlorophyll yet absorb slightly different wavelengths of light.

Other reports by Iphone Fresh

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