Scientists Warn that the Color of the Ocean is Changing Due to Climate Change
Beachgoers around the world would probably give different descriptions of the ocean. Those gazing at the Caribbean Sea might describe clear or turquoise water, while those along Argentina’s coastline, where major rivers empty into the Atlantic Ocean, could report a light brown, sediment-rich view.
But even though seawater has always differed depending on location, season, or currents, scientists say the color of more than half of the world’s oceans is changing — and fast.
A new study, published in Nature and conducted by researchers at the Massachusetts Institute of Technology, analyzed two decades’ worth of specialized satellite observations. The study found that the color changes in the oceans are a warning sign of human-driven climate change.
The main reason behind these changes is phytoplankton, the microscopic marine algae that reside in the water’s upper layer. Phytoplankton use a green pigment called chlorophyll to convert sunlight into food. This pigment is often seen from space and is the main indicator scientists use to study the ocean’s color. However, phytoplankton are highly susceptible to climate change, and their populations are being disrupted, causing the ocean’s color to change.
“These ecosystems have taken millions of years to evolve together and be in balance. Changes in such a short amount of time are not good because they put the whole ecosystem out of balance,” said Stephanie Dutkiewicz, a researcher at MIT and co-author of the study.
The researchers analyzed data from NASA’s Aqua MODIS satellite, which has been monitoring ocean color changes since 2002. The data from the past twenty years showed that colors had shifted in more than half of the world’s oceans, surpassing what is expected due to natural occurrences.
To determine whether this trend is related to climate change, the researchers compared their findings with the results of two models. One model simulated what would happen to the ocean’s colors without the influence of greenhouse gases, while the other model incorporated these emissions. The second model showed a shift in color in 50 percent of the ocean, consistent with the satellite observations.
The changing color of the ocean is a worrisome sign for the future of the planet, according to Dutkiewicz. “Now we can see it firsthand — we have a signal of it going on in the real world. And that’s frightening because it means it’s not just my computer saying this anymore: It’s satellite sensors saying, ‘Yes, the ocean’s color is changing and really fast.'”
The color of the ocean is influenced by various factors, including how light waves interact with the water’s molecules. The ocean’s composition and the nutrients it sustains determine its color. To observe and understand these variations, scientists rely on satellite observations.
In some areas, rising temperatures disrupt the flow of deep-sea nutrients that surface-dwelling phytoplankton require to survive, leading to a decrease in their populations and bluer water. In other regions, an increase in phytoplankton populations has caused the water to have a greener tint. These changes have far-reaching effects on the marine ecosystem and food chains.
While these changes may not be easily noticeable to the naked eye, they have the potential to impact the environment and human beings in various ways. It serves as a wake-up call to take immediate action against climate change.
“It’s almost like we keep pressing the snooze button on an alarm that’s telling us we have to act now,” said Dutkiewicz.