The blue planet is changing color driven by climate change. This is the result of a large-scale study by scientists, which was created with the help of satellite images from 20 years (2002 to 2022). The remarkable result: More than half of the oceans (56%) have changed color over a 20-year period. The general trend: The seas of the earth are getting greener and greener.
With the help of NASA’s Aqua satellite and the Moderate Resolution Imaging Spectroradiometer (MODIS), the scientists analyzed measurements of the ocean color. The satellite takes measurements at seven wavelengths, including the blue-green ratio, which researchers often use to estimate the amount of chlorophyll. The new, eye-catching study comes from the renowned MIT’s National Oceanography Center (NOC) and was funded with funds from NERC, NASA, Innovate UK (Horizon Europe) and Horizon 2020.
“The satellite data we examined show a change in color over a massive chunk of ocean, equivalent to a larger area than the entire landmass of Earth. The computer simulations we examined suggest that these color changes could be due to climate change. The hope is that this study will stimulate further investigation into the causes and effects of these changes,” said Dr. BB Cael, senior scientist in the Ocean BioGeosciences group at NOC and lead author of the study.
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Small plankton possibly as a reason
The reason why the seas are getting greener and greener is probably due to the plankton. The color of the ocean results principally from the substances that float in its upper layers. While there is very little life in the deep blue sea, a green color means there are ecosystems based on phytoplankton — those plant-like microbes that contain chlorophyll. This plankton forms the basis of food for krill, fish, seabirds and marine mammals. It is unclear why this plankton is now spreading to more and more marine regions. The study does not confirm, for example, that this has anything to do with the warming of the oceans – even if the assumption is reasonable.
In any case, the change towards smaller plankton is a cause for concern for the scientists. “This shift towards smaller plankton could be a concern in the future as it could make the ocean less able to store carbon. Plankton could account for between 5% and 17% of new carbon entering the ocean by 2100, according to the latest data from the IPCC. Smaller plankton are less able to store this carbon, potentially limiting its effectiveness.
Incidentally, the color change in the oceans cannot be observed with the naked eye, which requires huge amounts of data from satellite images.