A warming climate has changed the color of 56% of the world’s oceans: study

New York: An alarming study suggests that human-induced climate change has changed the color of 56 percent of the world’s oceans in the past 20 years.

In particular, tropical ocean regions near the equator have become steadily greener over time, the study, published in the journal Nature, reveals. Because ocean color is a direct reflection of the organisms and materials in its waters, a change in ocean color indicates that the ecosystems within the surface ocean must also change.

Scientists including the Massachusetts Institute of Technology (MIT) in the US and the National Oceanic Center in the UK have tracked changes in ocean color over the past two decades. .

These color changes, though subtle to the human eye, have occurred in more than 56 percent of the world’s oceans — a larger area than Earth’s total landmass.

„I’ve been running simulations for years that have been telling me that these changes in ocean color are going to happen. It’s not surprising, it’s scary to see them happen. These changes are consistent with human-induced changes in our climate,” said senior research fellow in MIT’s Department of Earth, Atmospheric and Planetary Sciences and Center for Global Change Science. said scientist Stephanie Dutkiewicz.

„This provides further evidence of how human activities affect life on Earth at a large spatial scale. Another way humans affect the biosphere,” said lead author BB Gale of the National Oceanographic Center in Southampton, England.

To understand the effect of climate change on the oceans, scientists have previously only monitored phytoplankton – abundant plant-like microbes in the upper ocean and the green pigment chlorophyll, which helps hold the base of the ocean food web and the oceans. and save carbon dioxide.

But they realized that detecting any trends specifically driven by climate change would require at least 30 years of continuous monitoring.

In the current study, Gale and team analyzed measurements of ocean color taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Aqua satellite, which has been monitoring ocean color for 21 years. MODIS takes measurements at seven visible wavelengths, including two colors that researchers traditionally use to assess chlorophyll.

The color differences picked up by the satellite are too subtle for the human eye to distinguish. Most of the ocean appears blue to our eyes, whereas the true color may consist of a subtle mixture of wavelengths ranging from blue to green and red.

Gale performed a statistical analysis using all seven ocean colors measured by the satellite from 2002 to 2022. He first saw how much the seven colors changed from region to region in a given year, which gave him an idea of ​​their natural variations.

He zoomed in to see how these annual variations in ocean color changed over two decades. This analysis produced a clear trend rather than the typical year-to-year variation.