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Environment | Acidic Oceans

Climate change is altering the colour of our oceans

Dr. Mario Picazo
Meteorologist, PhD

Friday, February 8, 2019, 4:50 PM - Climate change is transforming the world we feel and see, and a recent study published by researchers at the Massachusetts Institute of Technology (MIT) comes to prove those changes will be even more visible in decades to come.

Their research published in the journal Nature Communications shows how the color of the surface of our oceans and seas will be different by the turn of the century, although we will not have to wait so long to start noticing them.


This large transformation is being driven by minute aquatic microorganisms known as phytoplankton, which drift on surface waters and have a great photosynthetic capacity.

Not only do phytoplankton absorb large amounts of sunlight, but they are also the foundation of marine food chains that are essential for many species.

Global chlorophyll concentrations in Earth’s oceans as determined by satellites. (NASA Earth Observatory)

As greenhouse gas concentrations continue to rise, oceans become warmer and, consequently, more acidic.

Changes in these two variables directly impact phytoplankton populations. This means that the capacity of oceans to absorb or reflect solar radiation will also change, as will the color of surface waters.

In the future, subtropical oceans are expected to become more blue due to a decrease in the biomass of these organisms. Meanwhile, oceans in the Arctic and Antarctic regions will progressively become more green as conditions become more favorable for phytoplankton blooms.

The predicted changes have already been occurring and have been monitored during the past two decades by a couple of NASA satellites that keep an eye on our oceans.

The satellite data is then fed into computer models to predict chlorophyll levels (a pigment present in green phytoplankton and plants that absorbs solar radiation efficiently.)

In order to isolate the signal of anthropogenic climate change from natural climate variability, the study also includes episodes of El Niño and La Niña. These are also capable of producing significant variations in the concentration of chlorophyll around the world.

Other factors contemplated in the study include phytoplankton food sources and their growth rates, tied in with ocean circulation patterns.

This array of data eventually produces a forecast of ocean surface colors directly linked to phytoplankton populations.

Besides the color pattern changes predicted, the model also provides valuable information on the future concentration and distribution of phytoplankton. With an expected sea surface temperature rise of 3 C by 2100, half of the world’s oceans will experience this complex transformation of colors which is already in the works.

Beyond the visual aspect of our oceans and seas, there is another issue that appears to trouble scientists significantly – phytoplankton is the foundation of marine food chains, and climate change will modify those foundations all over the planet.

This large-scale change will eventually have a tremendous impact on marine species and, indirectly, on other animal and plant forms that depend on them.


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