Huge swaths of the world’s oceans have changed color in the last 20 years, demonstrating a slight greening towards the tropics that researchers think indicates the influence of climate change on life in the world’s seas. Scientists reported on Wednesday that they had discovered color alterations across more than half of the world’s oceans – a region larger than Earth’s total land surface.
The authors of the Nature paper believe this is due to changes in ecosystems, notably in small plankton, which are the centerpiece of the marine food web and play an important role in atmospheric stabilization. “The reason we care about the color changes is that the color reflects the state of the ecosystem, so color changes mean ecosystem changes,” lead author B.B. Cael, of Britain’s National Oceanography Centre, told AFP.
When viewed from space, the color of the oceans can provide a picture of what is going on in the upper layers of the water. A deep blue indicates that there isn’t much life, whereas greener water indicates greater activity, specifically from photosynthesizing phytoplankton, which, like plants, contain the green pigment chlorophyll. These produce a considerable amount of the oxygen we breathe, play an important role in the global carbon cycle, and form the foundation of the ocean food web.
Researchers widened the color range in the most recent study, examining seven hues of ocean color
Researchers are eager to develop methods of monitoring ecological changes in order to track climate change and establish protected zones. Previous research, however, revealed that three decades of ocean chlorophyll monitoring would be required to discern a trend due to annual changes. Researchers widened the color range in the most recent study, examining seven hues of ocean color observed by the MODIS-Aqua satellite from 2002 to 2022.
These are too faint for humans to detect and seem mostly blue to the naked eye. The authors examined the observational data for a trend that was greater than the year-to-year fluctuation, then compared it to computer models of what would be predicted with climate change. They discovered that the observed changes corresponded closely to the predicted changes. While the experts admit that further research is needed to determine the exact meaning of the color changes, they believe climate change is the most likely culprit.
“I’ve been running simulations that have been telling me for years that these changes in ocean color are going to happen,” said co-author Stephanie Dutkiewicz, of MIT’s Department of Earth, Atmospheric and Planetary Sciences at the Center for Global Change Science.
“To actually see it happening for real is not surprising, but frightening. And these changes are consistent with man-induced changes to our climate.”
