Over the past 20 years, more than half of the oceans have changed color, subtly turning from blue to green in some regions, highlighting the effect of climate change on life in the world’s seas, researchers have found.
According to a study published Wednesday in Naturethe change is due to a variation in ecosystems, and in particular plankton, which is the centerpiece of the marine food system and plays a crucial role in the global carbon cycle and in the production of the oxygen we breathe.
“The reason we are interested in color changes is that the color reflects the state of the ecosystem,” study lead author BB Cael, from the National Oceanographic Center of Grande, told AFP. -Brittany.
The color of the seas, seen from space, can indeed give an idea of what is happening in the upper layers of the water: a deep blue means that there is little life, whereas if the water is greener, there is likely to be more activity, especially from phytoplankton which, like plants, contain a green pigment linked to chlorophyll.
Far from being trivial, the evolution of phytoplankton and its concentration in certain regions, to the detriment of others where it could disappear, could upset the entire marine food chain.
Scientists therefore want to develop ways to monitor these changes in ecosystems in order to track climate change and establish protected areas.
The study of Nature expanded the color spectrum, examining seven ocean color hues monitored by the MODIS-Aqua satellite from 2002 to 2022. These hues are too subtle to be perceived by humans and appear largely blue to the naked eye .
Its authors compared observational data to computer models of climate change. They came to the conclusion that the observed changes corresponded closely to what had been predicted by the models.
“I’ve been doing simulations for years that tell me these ocean color changes are going to happen. Seeing this actually happen is not surprising, but frightening,” said Stephanie Dutkiewicz, study co-author and member of MIT’s Department of Earth, Atmospheric, and Planetary Sciences.
While further work is needed to determine the exact implications of the color changes, the study authors believe it is very likely that climate change is the cause.
“These changes are consistent with what is known about human-induced changes in climate,” Dutkiewicz said.